As is known, certain last-generation vehicles are equipped with a regulating device for fully automatically controlling air intake of the engine as a function of a number of vehicle/engine parameters supplied by respective sensors, and on the basis of the position of the accelerator control device (pedal or grip) set by the user.
The regulating device substantially comprises a throttled body connected to the engine and having a feed conduit along which the air intake by the engine flows; and a throttle housed inside the feed conduit and which rotates, on command, about an axis of rotation to regulate the air intake of the engine and so adjust the torque generated by the engine.
In the case in question, the throttle rotates about its axis between two limit positions corresponding to minimum and maximum air flow respectively.
The regulating device also comprises an electric actuator for rotating the throttle; a potentiometer connected to the throttle to determine its angular position; and an electronic central control unit which, depending on torque demand by the user and on the operating condition of the vehicle/engine, calculates a target angular position of the throttle and accordingly controls the electric actuator to set the throttle to the calculated target angular position.
A major drawback of the above regulating device is that any malfunctioning of the sensors and/or electronic components cooperating actively with the electronic central control unit to control the throttle impairs the precision with which the throttle position is controlled, and may create a certain amount of unease in the user when the throttle remains in a position allowing the engine to generate a higher torque than demanded by the user.
In which case, in fact, any attempt by the user to release the accelerator pedal (grip) to reduce air flow to the engine fails to produce a corresponding rotation of the throttle. In other words, in the event of electric throttle control failure, the user is unable to reduce the engine torque.
To eliminate the above drawback, it has been proposed to increase the number of vehicle and/or engine parameter measurements to achieve redundant data processing by which to safely control operation of the throttle. Besides complicating processing by the electronic central control unit, however, this solution calls for a large number of sensors, thus increasing the manufacturing cost of the regulating device.
EP-0089492 discloses an internal combustion engine for vehicle having at one cylinder, an intake manifold leading to cylinders, a fuel supply means, an accelerator, a first throttle provided in the intake manifold.
U.S. Pat. No. 4,637,487 discloses a traction control device in an engine which has an intake passage. The throttle valve and a flow control valve are arranged in series in the intake passage
EP-0659991 discloses an system for controlling the flow of air entering the intake manifold of a multi cylinder variable displacement internal combustion engine installed in a vehicle having a driver-operable accelerator control includes an accelerator control position sensor for determining the operating position of the accelerator control and for generating an accelerator control position signal indicating such position, as well as an engine speed sensor for determining the speed of the engine and for generating an engine speed signal indicating such speed.
U.S. Pat. No. 5,520,146 discloses an electronic controller for automatically adjusting the position of a throttle valve in either a signal valve or a series valve throttle mechanism.